Connection for a golf club shaft

ABSTRACT

This invention is a connection which can be used to secure a shaft in a hosel of a golf club head or a shaft extension in a golf club shaft. The connection uses tapered threads in its operation to expand a locking shaft inside a receptacle. This connection is easily-loosened and repositioned, readily allowing adjustment in total golf shaft length. It is especially suitable for use in converting a putter with a conventional shaft length into a longer shaft “belly putter”. It is low in cost to produce, requires few parts, and is easily adjusted using simple tooling.

This invention is a connection which secures a golf shaft in a hosel of a golf club head, or a shaft extension in a golf club shaft. This connection is easily loosened and repositioned, readily allowing adjustment in total golf shaft length. It is especially suitable for use in converting a putter with a conventional shaft length into a longer shaft “belly putter”. It is low in cost to produce, requires few parts, and is easily adjusted using simple tooling.

BACKGROUND—DESCRIPTION OF PRIOR ART

Putting can be the most frustrating part of many golfer's games, and they consequently often try many types of putters to improve this part of their game, including putters with different shaft lengths. Conventional length putters typically have overall lengths of 84 cm (33 inches) to 91 cm (36 inches) and are meant to be held only in the golfer's two hands. A putter with a longer overall length, typically 104 cm (41 inches) to 114 cm (45 inches), is commonly called a “belly putter”. The belly putter is held in the golfer's two hands but the end of the shaft is also placed in the golfer's navel, thereby helping stabilize the putter. Even longer putters are sometimes used in which the shaft end is placed in the sternum or even up to the chin.

If a golfer has been using a conventional length putter but would like to try a longer putter, a belly putter for instance, this can be a difficult and expensive task. Belly putters are not commonly found in golf pro shops and smaller golf retailers, and therefore it is not easy to “demo” one to see if it is a fit for the golfer. Usually the golfer must purchase a belly putter, from an on-line retailer for instance, and they are relatively expensive, typically more expensive than conventional putters. Also, there is no good way to determine which length belly putter would be optimum apart from purchasing one and using it for a while. If the one purchased is not correct, the golfer is faced which the purchase of another belly putter of a different length. This expense and difficulty in many cases prevents golfers from trying a belly putter to see if it would improve putting accuracy. A desirable product would be one which could easily and inexpensively convert an existing putter into a belly putter for instance, and would be adjustable in length to suit an individual golfer's swing.

Several mechanical golf club connections have been discussed in prior patents which could be applicable in this area, for instance U.S. Pat. No. 5,024,438 to Candow, U.S. Pat. No. 5,469,029 to Heath et. al., and U.S. Pat. No. 7,083,529 to Cackett et. al., but all these devices use a relatively large number of parts and are relatively expensive to manufacture.

OBJECTS AND ADVANTAGES

It is an object of this invention to provide a connection for a golf club shaft which is low in cost to manufacture and easy to install.

It is a further object of this invention to provide a connection for a golf club shaft which is easily adjusted to change the effective length of a golf club shaft.

It is a further object of this invention to provide a connection for a golf club shaft which is ideally suited for use in converting a conventional length putter into a belly putter with an adjustable shaft length.

It is a further object of this invention to provide a connection for a golf club which will not allow rotation in the connection.

Still further objects and advantages will become apparent from a consideration of the ensuing description and drawings.

BRIEF DESCRIPTION OF DRAWING FIGURES

FIG. 1 shows in perspective a connection of this invention, while

FIGS. 2 through 5 show in cross-section this connection assembly, more particularly showing tapered threads used in the connection.

FIGS. 6, 7, and 8 show in axial cross-section connections which will not allow rotation of the joint and

FIGS. 9, 10, and 11 show in cross-section connections which have enhanced ability to prevent connection separation.

FIGS. 12 and 13 show in cross-section connections of this invention used in golf clubs.

REFERENCE NUMERALS IN DRAWINGS

-   2 locking shaft with tapered internal threads -   2′ expanded locking shaft 2 -   4 locking shaft with straight internal threads -   14 slot -   16 tapered internal threads -   17 straight internal threads -   18 screw -   19 tapered screw -   20 receptacle -   21 splined receptacle -   22 axially pinned receptacle -   23 radially pinned receptacle -   24 tapered receptacle -   25 ringed receptacle -   26 stepped receptacle -   27 golf shaft -   28 hosel receptacle -   31 spline -   32 axial pin -   33 radial pin -   34 taper in receptacle -   35 ring -   36 step in receptacle -   40 golf shaft grip -   42 golf shaft grip hole -   44 locking shaft grip -   46 locking shaft grip hole -   50 conventional golf club head -   51 golf club head hosel -   52 drilled golf club head -   54 hole drilled in golf club head

DESCRIPTION AND OPERATION—FIGS. 1 TO 5, BASIC OPERATION OF THE CONNECTION

FIG. 1 shows a shaft connection of this invention, this connection having a locking shaft 2 with four slots 14. Shaft 2 has tapered internal threads 16 which will accept a screw 18. Shaft 2 is designed for insertion into a receptacle 20, typically a hosel in a golf club head or a hollow golf club shaft. FIGS. 2-4 show this connection, more particularly showing in cross-section tapered internal threads 16. In FIG. 2, screw 18 is shown at a location relative to tapered threads 16 wherein there is clearance between screw 18 and internal threads 16. FIG. 3 shows screw 18 deeper into threads 16 and just beginning an interference fit with tapered threads 16. FIG. 4 shows screw 18 even deeper in tapered threads 16 with locking shaft 2 deformed to expanded locking shaft 2′ due to the interference between tapered threads 16 and screw 18. Expanded shaft 2′ makes contact with receptacle 20. FIG. 5 shows a locking shaft 4 which has straight internal threads 17 used with a tapered screw 19 (with tapered external threads).

In FIG. 1, locking shaft 2 is inserted into receptacle 20, and if adjustability is desired, the outside diameter of shaft 2 should be smaller than the inside diameter of receptacle 20. Golf club shafts used for putters are normally made of steel and are tapered, and they have an internal diameter near the top end of about 14.2 mm (0.56 inches). For ease in adjustability, a suitable outside diameter for locking shaft 2 when receptacle 20 is a putter shaft has been found to be approximately 14 mm (0.55 inches). With this clearance, locking shaft 2 has been found to have a relatively wide range of insertion depths into receptacle 20 which in this case is a hollow putter shaft. A suitable material for locking shaft 2 is aluminum, but other materials will work such as steel, brass, or even a plastic. Four slots 14 are shown, but other numbers of slots 14 can be used, such as two or three. They can easily be cut into the end of locking shaft 2 using a saw for instance. A good screw choice for screw 18 is a hex socket cap screw.

FIG. 2 shows a screw 18 with straight threads positioned in tapered internal threads 16 where there is clearance between screw 18 and, threads 16; in other words, no torque exists in screw 18. This is a normal situation for internal and external threads; taps used to cut internal threads normally have a larger major diameter than their corresponding screws. To thread locking shaft 2, it has been found suitable to simply use a thread tap with a plug or taper chamfer on its leading end to cut tapered internal threads 16, but the tap is only partially run into the pilot hole in shaft 2. This causes some complete threads to be cut (about four complete threads are shown in FIG. 2) but also some incomplete threads are cut (also about four shown). In FIG. 2, screw 18 is only engaged in complete threads.

In FIG. 3, locking shaft 2 is shown at a different position relative to receptacle 20 than that shown in FIG. 2. Also, screw 18 is shown turned further into tapered threads 16 (shown about one turn more) to where the normal clearance between the internal and external threads just vanishes. This is the point at which there begins to be an interference between the internal and external threads and a torque can just begin to be applied to screw 18.

In FIG. 4, screw 18 is turned even further into internal threads 16, torque exists, and this torque energy is stored in the deformation of locking shaft 2 to shaft 2′ wherein the slotted portion of shaft 2′ is forced against receptacle 20. A frictional force therefore exists between shaft 2′ and receptacle 20 determined by the surface properties of shaft 2′ and receptacle 20 and by the force between these surfaces caused by the torque in screw 18. With sufficient torque, a frictional force will exist to lock shaft 2′ to receptacle 20 in the position shown in FIG. 4. Of course, the locking could have occurred at the position of shaft 2 relative to receptacle 20 shown in FIG. 2, showing how this connection can be used to adjust the effective length of a golf club shaft.

The deformation of shaft 2 to 2′ discussed above is ideally achieved at a relatively low torque in screw 18. Slots 14 essentially divide the slotted end of shaft 2 into cantilevered beams which have their ends bent radially outward as screw 18 proceeds into tapered threading 16. The strength of these “beams” is affected by the number and depth of slots 14, by the thickness of the “beam” (the wall thickness of shaft 2 in the area of threading 16 and slots 14), and the modulus of the material used to construct shaft 2. It has been found that a suitable design of shaft 2 having this sufficient “beam” weakness is a shaft 2 made from aluminum with an outside diameter of 14 mm (0.55 inches), an internal diameter of 12 mm (0.47 inches) giving a wall thickness of 1 mm (0.04 inches), four slots 14 with a width of 1 mm (0.04 inches) and a length of 18.5 mm (0.73 inches), and threading 16 cut using a taper chamfer tap UNF 5/16″-24 with a total thread length of 10 mm (0.4 inches).

FIG. 5 shows another way of achieving the same results; locking shaft 4 having straight internal threads 17 used with a tapered screw 19 with tapered external threads. In this case screw 19 is shown as being a hex socket set screw, commonly available as a tapered pipe thread plug. Of course, both internal and external threads could be tapered; for instance tapered screw 19 could be used with the tapered internal threads 16 of locking shaft 2 if desired.

DESCRIPTION AND OPERATION—FIGS. 6 TO 8, CONNECTIONS WHICH DO NOT ROTATE

FIG. 6 shows a connection which has locking shaft 2 inserted in a splined receptacle 21 which has splines 31 which engage slots 14 in shaft 2. FIG. 7 shows locking shaft 2 inserted in an axially pinned receptacle 22, receptacle 22 having a pin 32 which engages a slot 14. FIG. 8 shows locking shaft 2 inserted in a radially pinned receptacle 23, receptacle 23 having a radial pin 33 which engages two slots 14.

It is sometimes desirable when using this connection in a golf club shaft that the connection not allow rotation between the locking 'shaft and its receptacle. This is especially true if this connection is used to connect a golf club shaft to a golf head hosel and the golf club is an iron or wood, for instance. This is due to the fact that irons and woods attain very high swing speeds at impact with a golf ball. A torque is exerted on the connection between the club head and the shaft due to the fact that the shaft is located off-center from the impact position of the club head with the ball, and it is necessary in most cases that this connection resist this torque and not turn.

FIGS. 6, 7, and 8 show three ways to prevent rotation in the connection, all of them using slots 14 which were provided primarily to allow relatively easy deformation of locking shaft 2. In FIG. 6, receptacle 21 has been suitably machined to form splines 31 which can engage slots 14, thereby preventing rotation. In FIG. 7, axial pin 32 engages a slot 14 to prevent rotation, but of course other number of pins 32 engaging other numbers of slots 14 could be used. In FIG. 8, radial pin 33 engages two slots 14 to prevent rotation.

DESCRIPTION AND OPERATION—FIGS. 9 TO 11, RECEPTACLES WITH ENHANCED LOCKING PROPERTIES

FIG. 9 shows expanded locking shaft 2′ located in a receptacle 24 which has a taper 34 in its internal diameter. FIG. 10 shows expanded locking shaft 2′ located in a receptacle 25 which holds a ring 35. FIG. 11 shows expanded locking shaft 2′ located in a receptacle 26 which has a step 36 in its internal diameter.

When the connection of this invention is used to secure a golf club shaft to a golf head and the club is an iron or wood, relatively high swing speeds may make it desirable that the connection provide greater withdrawal properties than that normally achieved with a receptacle having a straight internal hole, as shown in FIG. 4, for instance. This can be achieved by providing a profile, or contour, in the receptacle in the area of the locking shaft. Three of the possible contours are shown in FIGS. 9, 10, and 11.

In FIG. 9, locking shaft 2′ is shown positioned in taper 34 of receptacle 24 when locked. If shaft 2′ tries to withdraw, thereby moving its expanded end to a position in taper 34 where the diameter of taper 34 is smaller than the diameter of the expanded end of locking shaft 2′, the compression force on shaft 2′ rises rapidly due to the resulting “squeezing” action of taper 34. The frictional force in the connection consequently also rises rapidly, hence the enhanced withdrawal characteristics. A similar enhancement in withdrawal properties results from the squeezing effect of ring 35 in FIG. 10 and step 36 in FIG. 11.

DESCRIPTION AND OPERATION—FIGS. 12 AND 13, GOLF CLUB CONNECTION EXAMPLES

FIG. 12 shows a connection of this invention used to adjustably extend the length of a golf club shaft 27 connected to a conventional golf club head 50 at a hosel 51. Shaft 27 has a grip 40 in which a suitable hole 42 has been provided to allow passage of locking shaft 2 into shaft 27, the receptacle of this connection. Locking shaft 2 optionally has a grip 44 with a hole 46 in its end. FIG. 13 shows a connection of this invention used to connect a golf club shaft 27 to a hosel receptacle 28 of a golf club head 52 in which a hole 54 is drilled to provide access to tapered screw 19. Hosel receptacle 28 is used with locking shaft 4, for instance, to make the connection of shaft 27 to head 52.

FIG. 12 shows by way of example one of the most beneficial uses of the connection of this invention; a conversion kit which adjustably extends a shaft of a conventional length putter so the putter can be used as a belly putter. The conventional putter includes the golf club head 50 (which in this case is a putter head), hosel 51 in which shaft 27 is attached (usually held in with an adhesive), and shaft grip 40. The conversion kit includes locking shaft 2 (shown as having a suitable overall length and outer contour to provide the necessary shaft extension adjustment), screw 18, and optional locking shaft grip 44. Grip 44 is provided with a hole 46 in its end to allow passage of a tool through grip 44 to turn screw 18. This tool can be a screwdriver if screw 18 has a slotted head, but it has been found preferable to use a hex socket cap screw for screw 18 and a T-handle hex key for its driver. To install the conversion kit, it is first necessary to provide hole 42 in the conventional golf club grip 40 of sufficient diameter to allow passage of locking shaft 2. Locking shaft 2 is then inserted the desired distance into golf club shaft 27 and locked by turning screw 18 with a suitable tool inserted through hole 46. It has been found that the connection is sufficiently locked in golf club shaft 27 which has a smooth internal diameter (no internal contour) at a relatively low torque on screw 18. The golfer can try various extension lengths of shaft 2 to find the length that suits his particular putting style. If the golfer decides that the belly putter is just not for him, the extension kit can simply be removed and hole 42 can be filled with a suitable plug (not shown).

FIG. 13 shows by way of example the connection of this invention used to attach golf club shaft 27 to hosel 28 of head 52. A suitable receptacle design for receptacle 28 is determined by the application of the golf club which is determined by head 52. For instance, if head 52 is a putter head, receptacle 28 can normally have a simple straight bore as shown in receptacle 20 of FIG. 5. If the head is an iron or wood which is subject to greater stresses than those occurring in a putter, then receptacle 28 may preferably be provided with an internal contour as in receptacles 24, 25, and 26 to increase its holding power. Receptacle 28 may also be provided with the anti-rotation devices as shown in receptacles 21, 22, and 23. Hole 54 is shown as passing through head 52 to access screw 19. Shaft 27 is normally relatively long, therefore requiring a relatively long tool to access screw 19 from the shaft end, but in some cases it may still be desirable have the driving means for screw 19 face the shaft. In this case hole 54 is-not required, and of course the driving means for screw 19 would need to face the shaft end.

SUMMARY, RAMIFICATION, AND SCOPE

Accordingly, the reader will see that this invention is a connection which uses tapered threads, internal, external, or both, to expand a locking shaft in a receptacle to secure the connection. The locking shaft is normally provided with slots in the area of its tapered threads to improve the locking action, and several embodiments are possible which prevent rotation in the connection and provide more positive locking, especially useful when the connection is used in golf irons or woods. It can be used to connect a club shaft to a hosel or to extend a golf club shaft. It has few parts, is low in cost to manufacture, and provides for easy length adjustment. This connection is ideally suited for use as an adjustable shaft extension to convert a conventional putter into a belly putter, for instance.

Although the description above contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. All the various combinations of receptacles, locking shafts, threads, screws, and other features discussed in this Application are too numerous to include here. Thus, the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given. 

1. In a golf club having a first part and a second part, a connection which joins the first part to the second part, the connection comprising, a portion of the first part which is a locking shaft with internal threads, a portion of the second part which is a receptacle in which the locking shaft is located, a screw with external threads which is threadably engaged in the internal threads of the locking shaft, a position of the screw relative to the locking shaft wherein an external thread of the screw has an interference with an internal thread of the locking shaft, whereby the locking shaft is deformed and thereby held in the receptacle.
 2. The connection of claim 1 wherein a portion of the internal threads are tapered.
 3. The connection of claim 1 wherein a portion of the external threads of the screw is tapered.
 4. The connection of claim 1 wherein the second part is a hollow golf club shaft.
 5. The connection of claim 1 wherein the second part is a golf club head and the receptacle is a hosel of the golf club head.
 6. The connection of claim 1 wherein the locking shaft can be held in a first position relative to the receptacle and the locking shaft can be held in a second position relative to the receptacle.
 7. The connection of claim 1 wherein a wall of the locking shaft formed by an external diameter of the locking shaft and its internal threads has a slot.
 8. The connection of claim 1 wherein the golf club is a putter and the receptacle is in a hollow putter shaft.
 9. The connection of claim 8 wherein the putter shaft has a conventional length.
 10. The connection of claim 8, wherein the connection is used to extend the putter shaft.
 11. The connection of claim 10 wherein the locking shaft can be held at a first position in the putter shaft and the locking shaft can be held at a second position in the putter shaft.
 12. The connection of claim 7 wherein the receptacle has a spline and the spline is positioned in the slot whereby a rotation of the locking shaft relative to the receptacle is restricted.
 13. The connection of claim 7 wherein the receptacle has a pin and the pin is positioned in the slot whereby a rotation of the locking shaft relative to the receptacle is restricted.
 14. The connection of claim 1 wherein a portion of the locking shaft has a first diameter before it is deformed and a second larger diameter after it is deformed, and a portion of the receptacle has a smaller diameter than the second larger diameter of the locking shaft, and wherein the portion of the locking shaft must pass the portion of the receptacle to separate the locking shaft from the receptacle.
 15. The connection of claim 14 wherein the receptacle contains a ring and the ring is the portion of the receptacle which has a smaller diameter than the second larger diameter of the locking shaft.
 16. The connection of claim 14 wherein the receptacle has a contour in its diameter and the contour has a taper.
 17. The connection of claim 14 wherein the receptacle has a contour in its diameter and the contour has a step. 